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40 diff into 60?

Discussion in '40- & 55-Series Tech' started by TMAN_FJ60, Jul 2, 2003.

  1. TMAN_FJ60

    TMAN_FJ60

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    I've got an 84 FJ60, and I've been contemplating going to 35" tires on it (currently 33/31, depending on season). Am I right that the 4.11 gears from a 40 will go in? What year did they change from coarse to fine spline? Also, will the powertrax locker i have go in the new diff? I'm thinking the whole third member swap would be easiest - would that work?

    TIA,
    Travis
     
  2. Cruiserdrew

    Cruiserdrew SILVER Star

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    It will work great for your 60. I've done it on mine. The FJ60 went to a different flange pattern in 85 but your 84 will line up without modifications. I used diffs out of a 1978, which I learned later are the most desirable ones because they have the 4.11 gears and a fine spline pinion. The coarse spline pinions are just fine too. What you don't want is a very early 3rd member with coarse AXLE splines. I don't know what year they switched over, but I think it was around 1968. And yes-the power trax will work. This is a great swap, and cheap too-I bought both diffs for $100. One other thing-I'd stay with the 33's, the 35's will be a bit much for a heavy wagon and 4.11's. Sure you can do it, but it will drive like a dog.
     
  3. TMAN_FJ60

    TMAN_FJ60

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    Thanks for the reply - what about the later 40s? Are they also fine spline pinions? Also, I should be ok with the 35s, if I do that - I forgot to mention I've got a 350 and a 700R4 tranny, so I've got enough power to do it :D. I've done the calculations, and if I remember correctly, the 35s with 4.11 gears would be in between 33s and 31s with the 3.70 gears that I have now, and it does fine with the 33s (albeit better with the 31s). &nbsp:Did you get the whole third member when you did yours? That would be the easiest, since I wouldn't have to bother with gear setup (something I haven't done). We're going on vacation to Colorado soon, so I'm going to check with Classic Cruisers on their prices. Thanks for the info!

    Travis
     
  4. CruisinGA

    CruisinGA

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    All 40's after '78 have 3.70's. '78 is the most desirable year.
     
  5. Landpimp

    Landpimp GOLD Star

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    79+ fj40's came with 3.70's stock.

    FWIW I used 4.11's ring and pinions(thanks Junk and JH) out of the rear of 2 fj80's(fzj same) when I went from 3.70 in my fj60, nice swap and makes more difference then you would think(as it's not a big jump numericaly)

    John H
     
  6. s79bj40

    s79bj40

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    my november '79 came stock with 4.11, so maybe you better check before you discount a donor.

    Sam
    '79bj40
    '76 serIII rover
    '6? serII rover
     
  7. Cruiserdrew

    Cruiserdrew SILVER Star

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    When I swapped, I got the complete 3rd members from a guy in Oklahoma. I really lucked out on the diffs which were in great shape. From the wear patern on the front, I doubt the donor rig had ever been in 4wd. The insides look new. The rear was good shape with minimal backlash. The swap took a long greasy weekend, but I got to repack birfs, change axle seals and the like. You have way more power than I and a flexible tranny so you should be fine with your 35's. I'm running 33's and the gearing feels perfect. Good luck.
     
  8. zuluzeugma

    zuluzeugma SILVER Star

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    probley a dumb question, but wont fj62 axles bolt right up under a fj60? I know this has been talked about before, but I'm kinda wondering right now.
    fj62 axles have 4.10 right?
     
  9. CruisinGA

    CruisinGA

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    62 axles have 4.11s and extra gusseting making them the strongest as well. &nbsp:Double whammy. But I can't answer your question about them bolting up. ???
     
  10. Cruiserdrew

    Cruiserdrew SILVER Star

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    The FJ62 diffs will work but the flange pattern will not bolt to the existing driveshafts. You could buy new flanges in the old pattern and/or drill to the correct spacing but that seems like a lot of work. If you had an 85 and newer FJ60 then the diffs from an FJ62 would work great.